Thermoplastic polyurethanes (TPUs) are prepared from diols and diisocyanates. See, e.g., D. Randall and S. Lee, “The Polyurethanes Book”, New York: John Wiley & Sons, 2003; and K. Uhlig, “Discovering Polyurethanes”, New York: Hanser Gardner, 1999. The isocyanate groups of the diisocyanate react with the hydroxyl groups on the diol to form a urethane linkage. The diol can be, for example, a low molecular weight polyether diol or polyester diol. The diisocyanate can be aliphatic or aromatic. The family of TPU resins is very complex because of the enormous variation in the compositional features of the diols and diisocyanates. This variety results in a large numbers of polymer structures and performance profiles. Indeed, TPUs can be rigid solids, or soft and elastomeric. TPUs are fully thermoplastic and can be melt-processed.
The generally recognized useful features of TPUs include high impact strength even at low temperatures, good abrasion resistance, good heat resistance, excellent resistance to non-polar solvents and fuels and oils, resistance to ozone and oxidation and humidity, and good electrical resistance. Less desirable features include high moisture absorption and lower rigidity at elevated temperatures.
There exists an opportunity for TPUs that exhibit improvements in one or more of reduced moisture absorption, increased heat resistance, and increased strength at high elongation.